<html>
<head>
    <script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery
/jquery-1.4.min.js">

        </script>

    <script type="text/javascript">
        $(document).ready(function(){
            $("button").click(function(){
                $("p").html("W3School");
            });
        });
    </script>

</head>


<body>
<h2>This is a heading</h2>
<p>This is a paragraph.</p>
<p>This is another paragraph.</p>
<button type="button">Click me</button>
</body>
</html>